The present invention relates to a data storage tape cartridge and associated tape path. More particularly, it relates to a data storage tape cartridge or tape path incorporating at least one idler wrap guide for limiting lateral storage tape movement during use.
Data storage tape cartridges have been used for decades in the computer, audio and video fields. Due to low costs and high storage capacities, data storage tape cartridges continue to be an extremely popular form of recording large volumes of information for subsequent retrieval and use.
One type of data storage tape cartridge consists generally of an outer shell or housing maintaining two tape reels, two or more corner guides, and a length of magnetic storage tape. The storage tape is wrapped about and extends between the two tape reels. The corner guides, in turn, articulate the storage tape through a defined tape path. In this regard, the tape path, as defined by the various corner guides, typically extends across a head access window (or read/write zone) formed in the housing. In particular, corner guides are positioned at opposite sides of the head access window to direct the tape path through the head access window. These two corner guides are typically xe2x80x9ccompliant guides,xe2x80x9d each providing an arcuate guide surface and opposing tape edge (or lateral) stop surfaces, one of which is compliant. Any remaining corner guides or guide surfaces are positioned to direct the storage tape between the tape reels and the corner guides associated with the head access window. Regardless, a door is normally associated with the head access window to provide selective access to the storage tape. During use, the data storage tape cartridge is inserted into a tape drive. The door is maneuvered into an open position and a transducer, such as a magnetic read/write head, engages the storage tape via the head access window. To ensure consistent, accurate engagement by the read/write head, the storage tape must be precisely positioned within the head access window.
Alternatively, single reel data storage tape cartridges are available and are well known in the art. Basically, upon engagement with the tape drive, the storage tape is directly away from the cartridge housing by internal components of the tape drive. For example, the storage tape may include a leader block that is configured to be engaged by the tape drive for directing the storage tape into engagement with the read/write head. With this design, the tape drive itself will include various internal guides for defining the desired tape path.
The data storage tape cartridges described above are normally operated (i.e., the tape reel(s) engaged and rotated to xe2x80x9cdrivexe2x80x9d the storage tape along the read/write head) in at least three different operational modes, including a start-up acceleration mode, a data transfer mode and a search mode. The effective tape speed varies for each mode. During the start-up acceleration mode, the storage tape is initially driven at a relatively low tape speed and accelerated. During the data transfer mode, a xe2x80x9csteady statexe2x80x9d tape speed is normally realized as data is read from or recorded to the storage tape. The data transfer mode tape speed is faster than that of the start-up acceleration mode. Finally, the search mode is employed to rapidly find data at a certain location along the tape length. As such, the search mode is typically performed at a much higher tape speed than that of the data transfer mode.
Regardless of the exact tape speed, various inherent design issues may compromise desired, precise positioning of the storage tape across the read/write head. For example, the tape reel(s) may contribute to unexpected lateral (or edge-to-edge) tape movement. In this regard, the typical tape reel includes a central hub and opposing flanges. The storage tape is wrapped about the central hub and is laterally constrained by the flanges (i.e., the flanges limit lateral movement of the storage tape by contacting a respective top or bottom edge). However, so as to not overly wear the storage tape edges, a slight tape edge-to-flange spacing is presented. That is to say, an overall lateral spacing between the opposing flanges is greater than a height of the storage tape, typically on the order of 0.002-0.01 inch. As a result, during tape reel rotation, the storage tape may move laterally from flange-to-flange. This is especially true during the data transfer mode in which the outermost layers of storage tape are normally not tightly wrapped about the tape reel hub. In other words, a xe2x80x9cslackxe2x80x9d is developed in the storage tape, such that the storage tape easily moves laterally between the opposing flanges. This unforeseen lateral movement is xe2x80x9cseenxe2x80x9d by the head, leading to read/write errors.
The corner guides cannot readily correct this unexpected lateral movement in that the guide surfaces associated with the comer guides are configured so as to not frictionally engage the storage tape at relatively high tape speeds, such as those encountered in the data transfer mode. Effectively, at tape speeds in the data transfer mode, an air barrier is generated between the guide surface and the storage tape such that the storage tape xe2x80x9cfliesxe2x80x9d over the guide surface. Thus, the guide surface does not frictionally dampen lateral tape movement. As previously described, compliant tape guides typically incorporate opposing, transverse surfaces that present xe2x80x9chard stopsxe2x80x9d to lateral tape movement. These transverse surfaces effectively angularly redirect lateral movements in the storage tape. In other words, a storage tape that has moved laterally along a tape reel will deflect at the associated compliant guide transverse surface, rendering the storage tape skewed or off-center with respect to the head.
Any slight deviation (or skew) from a desired planar positioning of the storage tape within the head access window may result in reading/writing errors. If the storage tape is slightly above or below an expected location, the read/write head will experience difficulties in finding a desired track on the storage tape. Additionally, the read/write head may encounter tracking problems whereby the head xe2x80x9closesxe2x80x9d a desired track. Importantly, with recent improvements in storage tape media that have increased available track densities, the likelihood of lateral movement-caused errors has similarly increased.
Data storage tape cartridges are important tools used to maintain vast amounts of information. While the evolution of cartridge components, including the storage tape and compliant guides, have greatly improved data storage tape cartridge capacity and performance, other unexpected problems, including lateral tape movement, have been identified. Therefore, a need exists for a data storage tape cartridge and tape path configured to dampen lateral storage tape movement during use, particularly in a data transfer mode.
One aspect of the present invention relates to a data storage tape cartridge comprising a housing, first and second tape reels, a storage tape, first and second comer guides and an idler wrap guide. The housing defines a head access window. The first and second tape reels are rotatably disposed within the housing, with the storage tape extending between the first and second tape reels. The first and second comer guides are disposed within the housing at opposite sides of the head access window for guiding the storage tape across the head access window. Finally, the idler wrap guide is disposed within the housing and defines a tape path extending from the first tape reel to the idler wrap guide, and from the idler wrap pin to the first corner guide. With this in mind, the idler wrap guide is configured to frictionally dampen lateral movement of the storage tape upon rotation of the tape reels. By dampening lateral storage tape movement, servo off track events are greatly reduced. In one preferred embodiment, the idler wrap guide is a pin forming a compound radius (or diameter) of curvature.
Another aspect of the present invention relates to a data storage tape cartridge comprising a housing, first and second tape reels, a storage tape, first and second corner guides and an idler wrap guide. The housing defines a head access window. The first and second tape reels are rotatably disposed within the housing, with the storage tape extending between the tape reels along a tape path. The first and second comer guides are positioned within the housing to direct the tape path across the head access window. Finally, the idler wrap guide is disposed within the housing along the tape path between the first tape reel and the first corner guide. In this regard, the idler wrap guide is positioned to engage the storage tape at a wrap angle of at least 30xc2x0. With this configuration, the idler wrap guide frictionally dampens lateral movement of the storage tape upon rotation of the tape reels.
Yet another aspect of the present invention relates to a method of using a data storage tape cartridge and tape drive. The method includes engaging the data storage tape cartridge within the tape drive. To this end, the data storage tape cartridge includes a housing, at least one tape reel rotatably disposed within the housing and a storage tape wound about and extending from the tape reel. The tape drive includes a read/write head. The storage tape is articulated through a tape path such that the storage tape engages the read/write head. The tape path is defined in part by an idler wrap guide. The storage tape is driven along the read/write head. In this regard, the storage tape is driven at different tape speeds for a start-up acceleration mode, a data transfers mode and a search mode. With this in mind, the idler wrap guide frictionally dampens lateral movement of the storage tape during at least the data transfer mode. The method is applicable to both single reel and dual reel data storage tape cartridges.
Yet another aspect of the present invention relates to a tape path for a storage tape of a tape cartridge engaged by a tape drive that includes a read/write head. During use, the storage tape is driven transversely along the read/write head. With this in mind, the tape path is defined in part by an idler wrap guide. The idler wrap guide is configured to frictionally dampen lateral movement of the storage tape as the storage tape is driven along the read/write head.